Which of these structures has dipole-dipole interactions? Water (H2O), ethyl alcohol (CH3CH2OH), and hexane (C6H14).
Water and ethyl alcohol will both have dipole-dipole interactions.
Technically they will both have Hydrogen bonding, which is a type of dipole-dipole. This is due to the high electronegativity values of oxygen atoms compared to the carbon and hydrogen atoms the oxygens bond to. This causes regions of both of these molecules that have partial negative charges and other regions wind up with partial positive charges.
Hexane will not have any dipole-dipole interactions because it is a non-polar molecule. The intermolecular forces between hexane molecules will be dispersion forces.